Objective To determine the feasibility of passive cooling to initiate therapeutic hypothermia before and during transport.

Methods Consensus guidelines were developed for passive cooling at the referring hospital and on transport by the London Neonatal Transfer Service. These were evaluated in a prospective study.

Results Between January and October 2009, 39 infants were referred for therapeutic hypothermia; passive cooling was initiated at the referring hospital in all the cases. Despite guidance, no rectal temperature measurements were taken before arrival of the transfer team. Cooling below target temperature (33°C–34°C) occurred in five babies before the arrival of the transfer team. In two of these infants, active cooling was performed, rectal temperature was not recorded and their temperature was lower than 32°C. Of the remaining 37 babies, 33 (89%) demonstrated a reduction in core temperature with passive cooling alone. The percentage of the babies within the temperature range at referral, arrival of the transfer team and arrival at the cooling centre were 0%, 15% and 67%, respectively. On arrival at the cooling centre, four babies had cooled to lower than 33°C by passive cooling alone (32.7°C, 32.6°C, 32.2°C and 32.1°C). Initiation of passive cooling before and during transfer resulted in the therapy starting 4.6 (1.8) h earlier than if initiated on arrival at the cooling centre.

Conclusions Passive cooling is a simple and effective technique if portable cooling equipment is unavailable. Rectal temperature monitoring is essential; active cooling methods without core temperature monitoring may lead to overcooling.